Open Access Issue
Algorithms for the Prize-Collecting k-Steiner Tree Problem
Tsinghua Science and Technology 2022, 27 (5): 785-792
Published: 17 March 2022

In this paper, we study the prize-collecting k-Steiner tree (PC kST) problem. We are given a graph G=(V,E) and an integer k. The graph is connected and undirected. A vertex rV called root and a subset RV called terminals are also given. A feasible solution for the PC kST is a tree F rooted at r and connecting at least k vertices in R. Excluding a vertex from the tree incurs a penalty cost, and including an edge in the tree incurs an edge cost. We wish to find a feasible solution with minimum total cost. The total cost of a tree F is the sum of the edge costs of the edges in F and the penalty costs of the vertices not in F. We present a simple approximation algorithm with the ratio of 5.9672 for the PC kST. This algorithm uses the approximation algorithms for the prize-collecting Steiner tree (PCST) problem and the k-Steiner tree ( kST) problem as subroutines. Then we propose a primal-dual based approximation algorithm and improve the approximation ratio to 5.

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